1. In a bowl, combine the mayonnaise, cumin and chili powder.
2. Without husking the corn, remove loose husks and exposed silk from each ear.
3. Place ears of corn, still in their husks, directly on a medium hot preheated grill. Cook corn in the husks, turning regularly, for about 6-8 minutes.
4. Remove the corn from the grill and "half husk," leaving the pulled back husks on the corn as a handle.
5. Brush the exposed corn liberally with 3/4 of the mayo mixture. Return the corn to the grill with the open side face up.
6. After the mayo mixture has melted into the corn, roll the corn over so the exposed kernel side is face down on the grill. Cook just long enough to add color to the corn.
7. Brush the corn with the remaining mayo mixture and crumble the queso blanco onto the open side of each ear.
8. Season with salt and pepper. Squeeze the juice of a lime wedge over each ear. Serve with an extra lime wedge and enjoy